Warm temperatures continue to weaken the snowpack. Skiers and riders triggered many avalanches on the buried weak layer in the last days. This layer can be triggered from a distance away, be mindful of slopes above and adjacent to you.
Strong south and southwest wind have formed wind slabs in lee terrain features at higher elevations.
Cornices might become weak with the warm temperatures. The additional load of a cornice failure can trigger a slab on the slope below.
The recent snow loaded a weak layer of surface hoar crystals found around 40 to 80 cm deep. The layer exists at all elevation bands and has recently been very reactive between 1600 and 2300 m. Example terrain features to particularly treat as suspect include the lee side of ridges, openings in trees, cut blocks, and burns.
Several avalanches on this layer were triggered from a distance away. Remote triggering is certainly a concern with this layer, watch out for adjacent and overhead slopes.
Warm temperatures will continue to weaken the snowpack and only slowly decrease during the day on Thursday.
WEDNESDAY NIGHT: Cloudy with clear periods, trace of new snow, light to moderate west wind, alpine temperature 0 C, freezing level 2200 m.
THURSDAY: Mix of sun and cloud, trace of new snow, light to moderate northwest wind, alpine temperature +3 C, freezing level slowly dropping to 1800 m.
FRIDAY: Sunny, trace of new snow, moderate northwest wind, alpine temperature -6 C, freezing level 1400 m.
SATURDAY: Sunny, light northwest wind, alpine temperature -1 C, freezing level 1500 m.
On Tuesday, skiers triggered several small slabs on the buried weak layer. One was triggered from a distance away. Just south of the region explosives triggered very large slab avalanches up to size 3 on the buried weak layer.
On Monday, skiers triggered several slab avalanches on the buried weak layer and avalanches also released naturally on this layer reaching up to size 2.5. The avalanches were 40-60 cm deep. Several cornice failures were reported and some triggered wind slabs on the slopes below. A deep persistent slab avalanche of size 2.5 was triggered by a machine and released on the early December facet/crust layer described in the Snowpack Summary.
On Sunday, skiers triggered large avalanches that released on the buried weak layer with surface hoar crystals. Check out some good example photos here. Some avalanches on this layer were triggered remotely. Several large and one very large (size 3.5) avalanche released naturally on the buried weak layer. The avalanches released at all elevation bands and all aspects. Explosives triggered numerous storm slabs up to size 2 below treeline on southeast aspects. Many large wet loose released naturally on sun-exposed slopes. Several large wind slab avalanches released naturally in the alpine and at treeline on east, south and west aspects.
The recent storm brought 10 to 30 cm snow. The snow has formed wind slabs with strong south to southwest wind in exposed terrain in the alpine and at treeline. A sun crust formed on sun-exposed slopes at all elevations.
The snow loaded a weak layer of surface hoar crystals 5 to 15 mm in size. The layer may be around 40 to 80 cm deep, which is a prime depth for human triggering. The layer is most prominent in areas sheltered from the wind. Example terrain features to treat as suspect include the lee side of protected ridges, openings in the trees, cut blocks, and burns. The layer may not exist on steep sun-exposed slopes, where a melt-freeze crust may be found instead.
The facet/crust layer that formed in early December is buried around 100 to 240 cm. The last reported avalanche was on February 7 in the southwest of the region. Although unlikely, the layer could be triggered from a large load like a cornice fall or a shallower slab avalanche could step down to this layer. Humans are unlikely to trigger it, with perhaps the exception in thin, shallow snowpack areas. Check out the forecaster blog for more information.
